The primary objective of the proposed research is to characterize the chemical changes occurring in the Escherichia coli cell envelope after infection with T4, and to associate these with functional changes known to occur. The functional changes of primary interest are: 1) the enhanced "leakiness" of the cell after phage attachment and its subsequent repair; 2) the development of resistance to lysis from without by high multiplicities of superinfecting phage; 3) the development of lysis inhibition; and 4) lysis from within. To correlate functional change with biochemical changes, E. coli cells will be infected with T4 mutants defective in these functions. Cell envelope preparations will be made from these cells and, after purification, they will be examined for chemical changes. In the chemical characterization, emphasis will be placed on the lipopolysaccharides of the outer membrane, and the proteins and phospholipids of both the inner and outer membranes.